It is known in the prior art to provide inflatable rubber boats or rafts with side sponsons that are tapered or pointed at their rear or stern ends. This construction allows undesirable instability which reduces the effectiveness of the driving mechanisms of the boat even before it has reached its gliding or planing speed. Some prior art rubber boats have wedge shaped sterns fastened to the undersides of the supporting sponsons across the stern for the purpose of stability and providing a favorable course or contour between the sponsons and the tapering sections. It has been demonstrated however that particularly in the case of a heavily loaded boat, there results only an inadequate streamlining effect from these stern connections.
In addition, sponson inserts or ring sockets of a different type than sealing or closure connections such as a straight rubber wall have been proposed. Under the influence of inflating pressure the sponsons and rings become constricted causing the rubber wall to arch toward the outside and as a result the streamlining is unfavorable because of the conical contour. With this construction no improvement of the streamlining is obtained even with the sponsons or pontoons that taper to a point.